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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 43: Wetting, Fluidics and Liquids at Interfaces and Surfaces (joint session CPP/DY)

CPP 43.5: Vortrag

Donnerstag, 21. März 2024, 16:00–16:15, H 0107

Interfacial versus confinement effects in the frequency dependent dielectric response of nanoconfined water — •Maximilian Becker and Roland R. Netz — Freie Universität Berlin, Berlin, Germany

We investigate the frequency-dependent dielectric response of water confined between two graphene sheets with force-field and density-functional-theory based molecular dynamics simulations. We highlight the critical role of the volume over which the dielectric response is averaged when measuring the dielectric susceptibility and introduce a system-size-independent decomposition, allowing us to discern interfacial and confinement contributions to the overall dielectric spectrum. Using this, we discuss the molecular origin of the main absorption features of nanoconfined water from the GHz to the THz regime: While intermolecular orientational correlations govern the interfacial and confinement effects on the 30 GHz Debye peak and the static dielectric constant, the 20 THz librational peak undergoes intensity changes which can be attributed to a change in single-molecule motion. When going from bulk to confinement, DFT-MD simulations reveal the emergence of a broad spectroscopic band arising between 1 and 30 THz, a region which is known to probe the dynamics of hydrogen bonds in water. These results are interpreted in the context of the hydrogen bond network at the water-graphene interface and in two-dimensional water layers which sheds light on the intricate behavior of water molecules within confined environments and contributes to a deeper understanding of their dielectric properties.

Keywords: Confinement Effects; Computational Spectroscopy; MD Simulations; Electrolytes at Interfaces